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Editor to share with you in the database design of the er diagram into a relational data model of the process belongs to what stage, I believe that most people do not understand, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

In database design, the process of transforming Emurr diagram into relational data model belongs to the "logical design stage". The Emurr diagram is used to describe the conceptual model of the real world, and the main work of the logical design phase is to design the conceptual data model of the real world into a logical pattern of the database, that is, to adapt to the logical data schema supported by a particular database management system.

The operating environment of this tutorial: windows7 system, mysql8, Dell G3 computer.

In database design, the process of transforming Emurr diagram into relational data model belongs to the "logical design stage".

Emurr diagram, also known as entity-relation diagram (Entity Relationship Diagram), provides a way to represent entity types, attributes and relationships, which is used to describe the conceptual model of the real world.

It is an effective method to describe the conceptual model of real-world relations. Is a way to represent a conceptual relational model:

The "rectangular box" is used to represent the entity type, and the entity name is written in the rectangular box.

Use "elliptical frame" or rounded rectangle to represent the attributes of the entity, and use "solid segment" to connect it with the "entity" of the corresponding relationship.

The "diamond box" is used to indicate the cause of the relationship between the entity types, and the name of the connection is written in the diamond box, and the "solid line segment" is used to connect with the relevant entity type respectively. At the same time, the type of connection is marked on the side of the "solid line segment".

Database design (Database Design) refers to the construction of an optimal database schema and the establishment of a database and its application system for a given application environment, so that it can effectively store data and meet the application needs of various users (information requirements and processing requirements). In the field of database, all kinds of systems that use database are often referred to as database application system.

The design content of database design includes: requirement analysis, conceptual structure design, logical structure design, physical structure design, database implementation and database operation and maintenance.

Demand analysis

Investigate and analyze users' business activities and the use of data, find out the type, scope and quantity of data used and their communication in business activities, and determine users' requirements for the use of the database system and various constraints, to form a user requirements specification.

Requirements analysis is on the basis of user survey, through analysis, gradually clarify the needs of users for the system, including data requirements and business processing requirements around these data. In the requirement analysis, the system is analyzed by the method of top-down and step-by-step decomposition, and the analysis results are graphically described by data flow chart (DFD).

Conceptual design

Through the classification, aggregation and generalization of the real world (which may be a factory, a shopping mall or a school, etc.) that users require to describe, an abstract conceptual data model is established. This conceptual model should reflect the information structure, the flow of information, the mutual restriction between information and the requirements of various departments for information storage, query and processing. The established model should avoid the specific implementation details of the database on the computer and express it in an abstract form. Taking the extended entity-(Emurr model) relation model as an example, the first step is to clarify the various entities and their attributes, the relations between entities and the constraints on information contained in various departments in the real world, so as to give a local description of the information used in each department (called the local view of the user in the database). The second step is to integrate the local views of multiple users into a global view, that is, the conceptual data model of the real world that the user wants to describe.

Logical design

The main work is to design the real-world conceptual data model as a logical pattern of the database, that is, to adapt to the logical data schema supported by a particular database management system. At the same time, it may be necessary to generate corresponding logical subpatterns for various data processing applications. The result of this step is the so-called "logical database".

Physical design

According to the physical design measures that depend on the specific computer structure, such as a variety of storage structures and access methods provided by a specific database management system, select the most appropriate physical storage structure (including file type, index structure and data storage order and bit logic, etc.), access methods and access paths for specific application tasks. The result of this step is the so-called "physical database".

Validate the design

On the basis of the above design, collect data and establish a database, and run some typical application tasks to verify the correctness and rationality of the database design. In general, the design process of a large database often needs to go through many cycles. When a problem is found at some step in the design, you may need to go back to the front to make changes. Therefore, the possibility and convenience of modifying the design in the future should be taken into account when doing the above database design.

Operation and maintenance design

In the process of formally putting the database system into operation, it must be constantly adjusted and modified.

Up to now, a lot of work of database design still needs to be done manually, except that relational database has a complete set of data paradigm theory which can be used to partially guide database design, there is still a lack of a set of perfect database design theories, methods and tools to realize the automation of database design or interactive semi-automatic design. Therefore, the future research and development direction of database design is to study the theory of database design, to seek data models that can express semantic relations more effectively, and to provide automatic or semi-automatic design tools and integrated development environment for each stage of design. make the database design more engineering, more standardized and more convenient, so that the database design fully reflects the advanced ideas and methods of software engineering.

These are all the contents of the article "what is the stage of converting er diagrams into relational data models in database design?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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